1. Field of the Invention
The present invention relates to a portable electronic device such as an IC card that is improved in IC module and IC module holding recess.
2. Description of the Related Art
An IC module for IC cards as shown in FIGS. 26 and 27 is known. FIG. 26 is a sectional view of the IC module and FIG. 27 is a diagram of the IC module viewed from the arrow in FIG. 26.
In FIGS. 26 and 27, reference numeral 21 indicates a substrate. The substrate 21 has an external terminal 21a on one side and an LSI 23 on the other side. The external terminal 21a has a terminal 24. The terminal 24 is opposed to a hole 21b formed in the substrate 21. The terminal 24 and LSI 23 are electrically connected to each other through gold wire 25 as a connection member. The LSI 23 and gold wire 25 are covered with a resin-made protection member 26 to be protected from external pressure. The IC module so configured is held and fitted into a holding recess formed in a card base.
However, conventionally, the protection member 26 is hemispherically formed and its central part is increased in thickness; therefore, it does not present strength problems but the following problem.
When the central part of the protection member 26 is thick, if the card base of the IC card is also thick, no problems occur. In this case, however, the card base is often thin. If, therefore, the protection member 26 is thick, the IC module cannot be held in the holding recess.
If the holding recess of the card base is formed deeply to excess, the IC module can be held therein. However, the inner bottom of the holding recess is thinned and cracked if a load is repeatedly applied to the card base.
To resolve the above problem, the protection member 26 of the LSI 23 can be formed to have a trapezoidal section and thus decrease in thickness, as shown in FIGS. 28 and 29. In this case, however, the following problems occur. The IC module in itself decreases in strength. If an external pressure such as bending and torsion is repeatedly applied to the IC card, the LSI 23 is destroyed or the gold wire 25 becomes poor in connection to thereby cause a malfunction.
Conventionally, the inner bottom of the holding recess of the card base is flattened. If an external pressure such as bending and torsion is applied to the IC card, stress is concentrated on the inner bottom of the holding recess. This concentration of stress causes problems that the card base is destroyed and the IC module is broken.